Automatic telephone system.



' G. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR; 55. 1910.

1,239,207.. Patented Sept. 4,1917.

ISHEETS-SHEET 1.

APPLICATION FILED MAR. 5, 1910.

Patented Sept. 4, 1917:

TSHEETS-SHEET 2.

vG. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR. 5. 1910.

1 39,207 Patented Sept. 4, 1917.

7 SHEETS-SHEET 3.

G. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR. 5. 1910.

1 ,39,207, Patented Sept. 4, 1917.

7 $HEETSSHEET 4.

G. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR. 5. 1910. 1,239.20? Patented Sept. 4, 191?.

'7 SHEETS-SHEET 5.

6. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAIL-5. 1910.

1 Q39 2Q7 Patented Sept. 4,1917.

1 SHEETS-SHEET 6.

*HIHIHIIIIIIIIIHIW G. E. MUELLER.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR. 5. I910- Patented Sept. 4, 1917.

ISHEETS-SHEET 7.

rennet Eric.

GEORGE E. MUELLER, or LA GRANGE, ILLINOIS, assxenon To KELLDGG swITcI-IBonnn ND SUPPLY COMPANY, OE CHICAGO, ILLINOIS, a CORPORATION or ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

- Specification of Letters Patent.

Patented Sept. a, tear.

Application filed March 5, 1910. Serial No. 547,454.

To all whom it ma concern Be it known that I, GEORGE E. MUELLER,

a citizen of the United States, residing La Grange, county-of Cook, Stateof Illinois,

have invented certain new and useful Improvements in Automatic Telephone Systems, of the following is a specification. 1 The present invention relates to automatlc telephone systems generally, and more particularly to that, type in which selector and connector switches are employed in conjunction with line selecting switches. In such systems, the switch structure is one in which movable contacts, or wipers, are associated with a large number of fixed or passive contacts arranged in a bank, and the wipers are first given a so-called primary move- -ment in one direction to bring them to a desired group of bank contacts, and then a so-called secondary movement to cause them to engage desired bank contacts in the selected group. In such a system,on the basis of ten thousand lines, 'ten per cent. trunking and hundred point switches, there would be one thousand line selectors, one

thousand first selectors, one thousand second selectors and one thousand connectors. Each subscribers line would be multipled to ten line selectors and ten'connectors. The line selectors and first selectors would have their wipers connected in pairs. The wipers of the second selectors would be multipled to the bank contacts of one hundred first selectors, and the wipers of each connector anism and circuits. To this end, I preferably do away with line selectors of the art which have primary and. secondany movements and replace the same by switches having simple rotary movements and a single driving means for a plurality of such.

switches and employ a novel arrangement of circuits in which ordinary telephone relays are used, to bring about the desired results. In working out my invention, I have necessarily provided apparatus and circuits which are capable of use in other systems than so-called full automatic systems and 1n other relations than those herein disclosed. With this general statement of the object and nature of my invention, 1 will now proceed with a detailed description of the same in connection with the accompany- 1ng drawings, and will then point out the scope of the invention more particularly in the appended claims.

Referring to the drawings, Figure 1, which includes Parts 1, 2 and 3, illustrates dlagrammatical'ly an automatic telephone system constructed in accordance with my invention; Fig. 2 is a plan of a line selector mounted upon a shaft common to other line selectors; Fig. 3 is aside elevation of the same, parts being broken away, and parts being shown in section; Figs. 4, 5 and 6 are elevations of a selector viewed from different sides; Fig. 7 is a plan view oi the same,

illustrating particularly the ofi-normal contacts; Fig. 8 is a sectional plan of the same taken on a plane indicated by the line 88 of Fig. 5; and Figs. 9 and 10 illustrate, respectively, in diagram, modifications of the line and line selector'clrcuits of Fig. 1.

I Main s /stem.

tion M and the called station N through the agency of line circuitX, line selector Q, first selector U, second selector V, connector W, and the line circuit X. Assuming that the selectors and connectors employed in establishing this connection areeach provided with one hundred bank contacts, and assumin that there are ten thousand lines in the exe ange, arranged on a basis of ten they have access.

per cent. trunking, then, as heretofore outlined, there would be one thousand line selectors Q, one thousand first selectors U, one thousand second selectorseV, and one thousand connectors W; The subscribers lines would be divided into groups of one hundred, and ten line selectors would be assigned to each group, thus enabling each line to be multipled to the corresponding bank contacts on ten line selectors. Each group of ten line selectors would be under the control of the one hundred lines to which Each subscribers line would also be multipled to the bank contacts of ten connectors which have access to the group of one hundred lines, in which said line is located. In the diagram, only two of the ten sets of multiple contacts of the line selectors and connectors are illustrated. The movable contacts, or Wipers, of each line selector Q are tied to the corresponding 'wipers of a first selector U, thus providing one thousand sets of connected line selectors and first selectors.

The wipers of the second selectors are multiply connected to bank contacts of the first selectors; and since there are one thousand of each of these switches, and each first selector has one hundred bank contacts, the wipers of each second selector are multiply connected to the corresponding bank contacts of one hundred first selectors. Sim- 'ilarly, the wipers of the one thousand connectors are multiply connected to the corresponding bank contacts of one hundred second selectors. As previously indicated, this oneof such line selectors extends the circuit .line belongs; the second operatifpn of the calling device causes this connected second selector V to advance four primary steps and then automatically to select an idle connector WV in the group of one hundred, to which the called line belongs; the third operation of the calling device causes the connector to advance five steps to that group line connections.

of ten contacts in which the called line is included; and the fourth and final operation of the calling device causes the connector to move over the contacts in that group to the sixth set of contacts, which are contacts of the called line. Thus connection is completed between the stations M and N. I

Each telephone line circuit X at the exchange is provided with a line relay LR and a cut-off relay CO; the first being effective to start a group of line selectorsto select a calling line, and the latter being efi'ective to destroy the normal substation control of the line relay and to otherwise change the Each line circuit also includes connections to the multiply connected contacts 30, 31, 32 and 33 of ten line selectors Q, as well as connections to the multiply connected contacts 49 50 and 51 of ten connectors.

In the case of the line selectors Q, I preferably employ ten switches for each group of one hundred lines and connect the ten sets of wipers of these switches to the common shaft 25. In the drawing, however, I have found it practicable to illustrate but two such line selectors Q. Obviously, the proportion of line selectors to the lines in a group may be varied at will. For each group of line selectors, I provide a common motor magnet MM, which, upon the initiation of a call, rotates the shaft 25 and moves the wipers of the idle line selectors Q of the group forward to seek connection with the calling line. Each line selector is provided with a clutch magnet CM, arranged to stopthe wipers upon connecting with the calling line. Each selector circuit also includes a release relay RR and a so-called connecting relay CR. Each line selector has four wipers which cooperate with asso-- ciated passive contacts. Two of these sets are illustrated in Fig. 1; the wipers of one set beingdesignated 26, 27, 28, 29, and those of the other 26 27 28 29 while the corresponding associated bank contacts are designated 30, 31, 32, 33, and 30 31 32 33 Each of these sets of wipers is angularly displaced with reference to the adjacent set, so that the wipers of the ten line selectors of the group are angularly different distances from a given starting point, producing a sort of spiral arrangement of the sets of wipers about their common shaft. Conseg rently, in operation, as the common shaft is rotated, the several sets of wipers will not engage their bank contacts simultaneously, but one set will engage its contacts before the others and that one will stop with its wipers in engagement with the bank contacts of the calling line.

Each first selector U includes wipers 34, 35, 36, arranged to cooperate with bank contacts 37, 38, 39, in response to the operation its ' of a primary magnet PM, controlled by the primary relay PR, and the secondary magnet SM, controlled by the secondary relay SR, .and the switch is released through the ondary movements of the wipers, respec tively. The circuit associated with this first selector. switch also includes the reversing relay RVR for reversing the direction of battery flow supplied to the calling line.

Each second selector switch V includes the wipers 40, .41, 42, with their associated positioned two steps below the first bank,

bank contacts 43; 44', 45. The wipers partake of the same primary and secondary movements as the first selector, and the relays, magnets and' off-normal springs are designated by primed reference characters corresponding to those of the first selector. y

Each connector W includes wipers 46, 47, 48, cotiperating with the bank contacts 49, 50, 51, and in this switch, as in the others, they partake of both the primary and secondary movements in response to the operation of the primary magnet PM and the secondary magnet SM respectively, and return to normal upon the operation of the release relay BB and the release magnet RM In this instance,.the primary ofinormal contacts are designated PONZ and the secondary ofi-normal contacts are designated SON? In addition to these parts, the circuit is'provided with a busy relay BR, a

ringing relay RG, a control relay R, a tip relay TR, a so-called flip-flofp relay FF,

and a closing relay CR, all 0 which 006perate in a manner hereinafter described. The secondary off-normal springs SON are so arranged that upon the first secondary movement'of the connector, contact spring 52is moved into engagement with its alternate contact, and spring 53 is moved out of engagement with its normal contact, and then upon the second step, said spring 53 is movedinto engagement with its alternate contact; and in this switch, the wipers are contact so that it requires two secondary steps to bring them into engagement with the first set of bank contacts. The line circuit X of line S is the same as the line circuit X of the line SP.

- The substation equipment at the subscribers stations M and N includes the customary switch-hook 54, receiver 55, transmitter 56, call-bell 57, condenser 58, impedance coil 59, and calling device 60. 1

Operation,

Having now given ageneral description of the character of the apparatus diagramthe number of the latters telephone is 3456,

the subscriber at M removes his telephone 55 from its switch-hook 54, thereby closing circuit from the live-side of battery B, through resistance coil .61, armature 62, conductor L limb S, winding of magnet 59, switchhook 54, transmitter 56, limb P, conductor L, armature 63, line relay LR to ground. This energizes the line relay which locks itself through armature contact 64, contact 65 of the cut-ofl' relay CO and resistance coil 61,, to the live side of battery B. A circuit is therefore closed through motor magnet MM from generator G, through contact 66, contact 67 to ground. The motor magnet hm thereupon steps the common shaft 25, with its attached sets of idle line selector wipers, forward to select the calling line. In theillustration, I have shown two sets ofwipers, but in practice 1 preferably employ ten sets, as previously stated. As the wipers 2c, 27, 2s, 29, and 26 27 28 29 step forward to seek connection with the calling line, on account of the spiral disposition of the wi ers previously pointed out, the wipers 26, 2 28, 29 will be the first set to reach contacts 30, 31,32, 33 of the calling -line. Upon the energization of line relay LR, circuit is closed from the live pole of battery B, through cut-ofl' relay CO, through contact 68 of relay LR to bank contact 31 As soon as wiper 27 connects to bank contact 31, clutch magnet CM is energized by a circuit from ground at contact 69 of relay 11 R, through the winding of clutch magnet CM, wiper 27, contact 31 and along the previously described path to battery B and no stops wipers 26, 27, 28 and 29 in engagement with contacts 30, 31, 32 and 33, respectively. As this circuit includes both the windings of clutch' magnet CM and the cutofi relay C0 both are energized. Upon the energization of cut-ofi' relay CO, the locking circuit for the line relay LR is opened at contact 65, restoring line relay LR to normal. The circuit for the motor magnet MM is opened at contact 67, thus preventing fur- 12o .ther operation of the said magnet.

relay CO, to the live pole of battery B.

The cut-0E relay C0 and. clutch magnet CM aft . now remain ener ized until the calling subscriber restores his telephone for disconnection. Upon the energization of clutch magnet CM, a circuit is also established from battery B (Fig. 1, Part 2), through pr1- mary relay PR, contact 71, conductor L contact 72 of relay (3 R, contact 7 3, conductor L contact 7 4 of relay RVR, the winding of secondary relay SE to battery B. Relays PR and SR are now energized and a circuit is established from ground at contact 7 5 of primary relay 1 R, contact 76 of relay 0 R, through the winding of said relay to the live pole of battery B. Relay (PR now becomes energized and a locking circuit is established through contact 77 to ground at contact 78 of clutch magnet CM. Upon the energization of relay (3 R, the aforesaid circuit through the primary and secondary relay is interrupted at contact 72 of relay (1 R, but is closed through contact 79, conductor L of switch Q, wiper 28, contact 32, conductor L of circuit X, limb P, transmitter 56, switch-hook 54, winding of magnet 59, limb S, conductor L contact 33, wiper 29, contact 80 of relay 6 R, and conductor L thus putting the primary relay PR and secondary relay SR directly under the control of the calling subscriber.

Assuming now that another subscriber in this same group, whose line terminates at contacts 81, 82, 83, 84, desires a connectlon, the removal of his telephone from its hook operates the line relay associated with h1s line and thereby closes a starting circuit for the motor magnet MM through the common connecting point'85. Thereupon the motor magnet MM advances the common shaft 25 until the wipers 26 27 28 29 connect ,with contacts 81 82 83 and 84 whereupon the same circuit changes take place in the line circuit associated with contacts 81 82 83 84 and the line selector circuit associated with wipers 26 27 28 29 as was described in the previous connection. From this description, it will be seen that, on a basis of ten percent. trunking, it is possible in each group of onehundred lines, to have ten simultaneous connections.

Having had his circuit extended through to the first selector U and the relays PR. and

' SR placed under his control, the calling subscriber first operates thedial 60 of his movement of the dial from normal, contacts 88, 89 and 90 are brought into engagement and remain so until the dial is restored again to normal. Accordingly, upon the return of the dial to normal, contact 86 opens the connection of line limb P to ground at 89 three times, followed by a single opening of the connection of the line limb S to ground at 89 once. The three primary impulses, thus given, actuate the primary relay PR three times, and the single secondary impulse actuates the secondary relay SR once. At the substation, magnet 59,through its armature fitting into a notch in the disk 60, normally locks the same against rotation. However, as previously noted, as soon as the circuit for the primary and secondary relays PR and SR is completed through the substation, magnet 59 is energized to attract its armature and thereby unlock the dial. This locking of the dial is for the purpose of preventing its operation until the .line circuit has been extended to a first selector. In the above operation, as soon as the dial is moved off normal, the single circuit for relays PR and SR through the substation is replaced by two circuits over the two sides of the line to ground at contact 89. One of these may be traced from battery B through the winding of relay PR, contact 71 of relay RVR, conductor L wiper 28, contact 32, limb P, primary springs 86, springs88 and 89 to ground; and the other from battery '13, through the winding of relay SR, contact 74, conductor L wiper 29, contact 33, limb S, secondary springs 87, contact springs 90, 89, to ground. Upon the return of the dial to normal, the

circuit from primary relay PR toground at 89 is interrupted three times at prlmary contact springs 86, dee'nergizing and energizing the primary relay PR three times, as above noted. Upon each deenergization of relay PR, a circuit is traced from ground at contact 91,"through contact 92, conductor L secondary ofi'normal contact 93, primary magnet PM to the live pole of battery B operating the primary magnet three times and stepping the wipers 34, 35, 36 to the third group of bank contacts which are multiply connected to second selectors in the third thousand group of lines. Following the primary impulses, the single secondary impulse decnergizes and energizes the secondary relay SE a single time; the pre viously described circuit frombattery B, through secondary relay SR to ground at contact spring 89, being interrupted a single time at secondary impulse springs 87 Upon the deenergizing of the secondary relay SE, a circuit is completed from ground at con tact spring 94 of the primary relay PR, contact 95, conductor L secondary oif-normal contact 96, primary oft-normal contact 97 which had closed upon the first primary to the first set of contacts in the bank had.

been previously selected, a ground (or busy) condition would have been placed upon the multiple contacts 37 by the first selector which had connected thereto, as will be hereinafter described. Thus upon wiper 34 engaging the first contact 37, which we have assumed has already been selected, a locking circuit for relay PRR is established from the live pole of battery B through the winding aof relay PRR, contact 100, contact 101 of relay RR,-contact 102 of release magnet RM, wiper 34, multiple contact 37 to the wiper 34 of the first selector which is connected'thereto, contacts 102, 101, and normal contact 100' to ground, The relay PRR remaining energized, secondary magnet SM steps the wipers 34, 35, 36 along to the next set of contacts in the bank and, assuming that they are connected to an idle second selector, relay PRR deenergizes and opens the energizing circuit for secondary magnet SM at contact 98, stopping the wipers 34, 35, 36,, which are now in engagement with contacts '37, 38, 39 of second selector V.

The subscriber now operates his calling device once more to send four primary impulses, to be followed by the single secondary impulse. Primary relay PR now energizes and deenergizes to send four impulses from ground at contact 91, through contact 92, conductor L contact 103, wiper 35 and contact 38, conductor L, secondary off-normal spring 104, through the winding of primary magnet PM of second selector V, to the live pole of battery, B thus energizing and deenergizing primary magnet PM four times and stepping the wipers 40, 41, 42 to.

the fourth group of bank contacts; This is followed by the secondary impulse to deenergize secondary relay SR a single time, and a circuit is now established from ground at contact 94 of primary relay PR, through contact 95, conductor L contact 105, wiper 36, bank contact 39, conductor L secondary off-normal spring 106, primary off-normal spring 107, which closed upon the first primary movement of the switch, the winding 1 of relay PRR live pole of battery B The relay PRR now becomes energized and moves its armature contacts to their alternate position. A circuit is now established 109, through the winding of secondary magnet SM to generator G, causing the wipers 40, 41, 42 to advance a single step to engage the first set of contacts 43, 44, 45. Assuming the first two sets of contacts in the bank leading to connectors similar to W have been previously selected, a grounded or busy condition would have been placed upon the multiple contacts 43 of the connectors re ferred to, as hereinafter described. As soon as the wiper 40 engages bank contact 43 of the first busy connector, alocking circuit for relay PRR is established along the following path: from the live pole of battery B through the Winding of relay 'PRR contact 110, contact 111 of release magnet RM wiper 40, the multiple contact 43 to the contact 43 of the busy cohnector W, through wiper 40 of the second selector connected thereto, contacts 111,112 and normal contact 108 of said second selector, to ground. Relay PRR remaining energized, the secondary magnet SM steps the wipers 40, 41, 42 to the second set of contacts, and assuming these to be busy also, relay PER remains energized and magnet SM steps wipers 40, 41, 42 to engage the third set of contacts 43, 44, 45 of the idle connector W. The locking circuit for relay PRR now being interrupted, due to' wiper 40 having reached a contact of an idle connector, the said relay PER- deenergizes and interrupts the circuit for secondary magnet SM at contact 113.

It will be noted that while the wipers 35 and 36 of first selector U are moving over contacts 38 and 39 of busy second selectors V, they are disconnected from first selector U at contacts 103 and 105 of relay PRR. This is to prevent first selector U from interfering with any established connection over which the wipers 35 and 36 are passing when stepping forward to select an idle sec ond selector. This is also true of the'wipers 41 and 42 of second selector V, which are disconnected at contacts 114, 115, of relay PRR when the said wipers 41 and 42 are passing over contacts 44 and 45 leading to busy connector switches W.

The calling subscriber M now having established connection switch W which has access to the one hundred lines in which the called line is located, he operates his dial to transmit five primary impulses, to be followed by a single secondary impulse. The primary relay PR,-

with the connector pulses from ground at contact 91, over the previously described path to Wiper 41 of second selector V, through contact 44,1seco'ndary off-normal contact 52 of connector 'W, through the winding of primary magnet PM", to the live pole ofbattery B energizing and denergizing primary magnet PM to step the wipers 46, 47, 48 of connector W to the fifth group of bank contacts in which the line of subscriber N terminates. first movement of the connector switch W, the primary off-normal springs PON move to their alternate POSltlOH and contact.

springs 116, 117, 118 engage their respective contacts. Following the primary impulses just described, a singlesecondary impulse is sent, deenergizing and energizing secondi ary relay SR, which transmits one impulse of current from ground at contact 94 over the previously described path to wiper 42 of second selector V,.contact 45, secondary off-normal spring contact 53, primary oli- -normal contact spring 117 through the winding of secondary magnet SM 'to the live pole of battery'B, to step the wipers '46, 47, 48 forward one step. The Wipers of the conne'ctorsw'itch W, as before noted, are

' adjusted in such avmanner that it requires two secondary steps to connect to the first set of bank contacts. As the wipers 46, 47, 48 have only been advanced one step, the are still one step-from the first set of ban contacts, but the following changes have.

taken place in the .secondar oil-normal spring contacts. Secondary 0 -normal con-,

tact 52upon the first secondary movement of the switch has advanced to its alternate position and made connection to its alternate contact. Contact spring 53 has moved out of engagement with its normal contact,

but as yet has not engaged its alternate contact, which doesnot occur until the second secondary step. 7

The calling subscriber, now having ad-i vanced the connector switch W to the group often lines which include the line extending to substation N, operates his calling device 60 to send six primary impulses, to'be followed by a secondary impulse, to advance the wipers 46, 47 and 48 to make connection with the bank contacts 49, 50 and 51 of the called line,'namely, that extending to substation N. Upon the operation of the dial,

the primary relay PR is denerg ized and energized six times and thereby six impulses of current-are transmitted from ground at contact 91, over the previously described path to secondary elf-normal contact 52 of connector switch W: Circuit now may be traced along conductor L, contact 119 of relay B, through the winding of secondary magnet SM to the live pole of battery-B energizing and deenergizing secondary magnet SM to advance the wipers 46, 47 ,48 six steps to connect with the bank contacts 49, 50, 51, which are the terminals ,of the called line N, which we have asshmed is .number 3456. Following the last primary impulse, a single-secondary impulse is transv mitted from the secondary. relay .SB, as

On the previously described, to contact 53 of secondary off-normal springs on connector W, .through its alternate contact which it engaged on the second secondary step, along "CR of connector W, which I will term the closing relay.

Gallant Zine idle.

We will now assume that the called line is in an idle condition. Upon the energi- ,zation of the busy relay BR, caused by the last secondary impulse, the upper winding of said relay is connected through alternate contact 121 to the wiper 46, and as we have assumed the called line to be idle, the circuit X is in the condition shown and," no lock ing circuit being established for the busy relay BR, it will deenergize and restore to normal upon the cessation of the last sec ondary impulse. It will be noted that upon the energization of relay BR, contact 122 of said relay .is momentarily closed. This is for the purpose of establishing a circuit from ground at contact 123 of relay BB through said contact 122, through the winding of relay R to the live pole of battery B energizing said relay R, which locks itself through contact 124 to ground at contact 123 of relay RR It will be noted that upon the energization of relay R, the busy relay BR and the secondary magnet SM are cut off from the line at contacts 119 and 120 of relay R. Upon the denergization of relay BR, a circuit is established from the ground at relayRG through the winding of said relay, contact 125 of relay R, normal contact 121 of relay BR, wiper 46,

bank contact 49, the winding of cu-t-ofi' relay CO to the live pole of battery B thus energizing both relay RG and relay CO. The energizing of relay CO disconnects the line relay LR and the live pole of battery B from the line. The energization of relay RG establishes a connection from ground at interrupter I, through contact 126, contact 127 of relay OR, the winding of flipfiop relay FF, to the live pole of battery B causing the said relay FF to attract and retract its armature 161 to periodically project ringing current from generator G out' over limb P through the call-bell 57 condenser 58, back over limb S bank contact 51 and wiper 48, contact 128 of relay- RG,

and winding of impedance coil 129, returning to the ground at, generator G, through the battery B and its ground connection. and ringing the call-bell of substation N.

The called subscriber, in response to the call, now removes his telephone from its switch-hook and a circuit is established from ground a tip relay TR, through the winding of said relay, contact 130, contact 161 of relay FF, wiper 47, bank contact 50, limb P through substation N, back over limb S contact 51, wiper 48, contact 128, through the winding of impedance coil 129 to the live pole of battery B,-thus energizing tip relay TR, which now remains energized and is directly under the control of the called subscriber N. Upon the energization of tip relay TR, a circuit is established from ground at contact 131, through the winding of closing relay CR, to the live pole of battery B thus energizing relay CR, which is now locked over a circuit established from the live pole of battery B through the winding of relay CR, locking contact 132, to ground at contact 123 of release relay RR The circuit through relay FF is interrupted at contact 127 of relay CR and relay FF thereby deenergized. Likewise complete connection is established between substations M and N by the closing of contacts 162 and 133 of closing relay CR. With the connection thus established for conversation, transmission current to the calling substation M is supplied from the battery B B, and to the called party from battery 13 over the previously described path, which includes impedance coil 129 and tip relay TR. A. grounded or busy condition is also placed upon the bank contact 49 and all of its multiples, traced from the ground through the winding. of relay RG. This is to prevent any other subscriber from making connection to the called line, as I shall now describe.

Called Zine busy.

Now, if it be assumed that the called line is busy by reason of some other connection to it, then, as previously stated, the bank contact 49 will be connected to ground through the winding of the tip relay TB of the connector which is connected to a multiple of contact 49. In such event, following the last secondary impulse, the busy relay BR, which had been momentarily energized through its lower winding, remains'locked, by a circuit traced from the ground at con tact 49, through wiper 46, alternate contact 121 and the upper winding of relay BR to the live pole of battery B The relayBR now remainingenergized, a busy signal is transmitted back to the calling subscriber from the secondary winding of induction coil 10, through condenser 134, closed contact 135 of busy relay BR, back over the upper heavily traced conductor, limb P, through the receiver and condenser at the calling substation M, back over the limb S to ground through connections to conductor the like, at the callingsubstation.

L Due to the characteristic busy signal, the calling subscriber will know that the line desired is not available for connection thereto. He will therefore restore his telephone to its switch-hook to cause the release and restoration of the switches and circuits to normal, as will be hereinafter more fully explained.

Before entering upon a description of the release operation, I will first call attention to the operation of reversing relay RVR associated with the first selector U. The purpose of this relay is to reverse the-direction of battery flow over the calling line and it is brought into operation upon the response of the called party. Such reversals are commonly employed for operating coincollecting mechanism, metermechanism, and I This operation of relay RVR is brought about in the following manner. Upon the response of the called subscriber N, a circuit is established from the live pole of battery B at first selector U, through the winding of relay 136, alternate contact 137 of secondary relay SR, along the lower heavily marked conductor, out over limb S through the telephone of the called substation N, back over limb P bank contact 50, wiper 47, normal contact 161 of relay FF, closed colitact 130 of relay RG, through the winding of tip relay TR to ground. Relay 136 of first selector U now being energized, a circuit is established from ground at contact 138, through the winding of reversing relay RVR to the live pole of batter B The connections of battery B B, t rough the rimary relay PR and the secondary relay R to the respective conductors L? and L are reversed, due to the closing of armature contacts 139 and 140 of reversing relay RVR. Relay RVR now is locked up by a circuit established through contact .141 toground at primary ofi-normal contact 142, which closed upon the first primary movement of the switch. A locking path is also established from the connection to ground at contact 143 of relay PR, the purpose of which will be explained later on.

Release,

Having now fully described the connection from a calling subscriber to both an idle and a busy called subscriber, the next step naturally leads to the consideration of the release of the switches employed in making' the connectionsjust described. The circuits of the difierent switches, used --in mak 'ing the connections, are so arranged that where a connection has been-completed for conversation between two subscribers, should the calling subscriber'b'e the first one to restore his telephone to thehook, the line circuit, line selector switch, first selector, and second selector will. restore to normal, but

the release of the connector in this instance is under the control of the called subscriber and is restored to normal when-he replaces the receiver upon its hook. Should the called subscriber be the first one to .restore any time, not to complete any connection once started he may replace his receiver upon its hoo and all switches, which have been operated up to that time, will be released.

Now, considering the releasing operations just described more in detail, it will be remembered that the relays PR and SR remain energized, due to a circuit established over the line and through the substation of the calling subscriber M. The 'conversajtion being finished, we will now assume that the calling subscriber is the first to" replace his telephone upon its switch-hook. Relays PR and SR are now deenergized and close their contacts 144, 145, and establish a releasing circuit, traced from ound at release relay RR of first selector U, through the winding of said relay, contacts 145,144, contact 146 of relay 0 R, and the windin of release relay B B of the line selectorto the live pole. of battery B. The release relay RR and RR are now energized to effect the release of the line selector andfirst selector. Due to the energization of the release relay RR of line selector Q, the

,'circuit from ground at contact 69, through the winding of clutch magnet CM and cutofl' relay CO is broken and the said clutch magnet and cut-ofi' relay are deener 'zed. The .deenergization of clutch magnet M is instrumental in restoring the relay C R to normal, due to the brea ing of its locking circuit at contact 78. The said clutch magnet also releases its hold upon th wipers 26, 27, 28, 29 of the line selector, and the release relay R R having den'ergized upon the breaking of its energizing circuit at contact 146 of relay C R, all parts of the lineselector Q, are restored to normal and. again it is available for connection'to any calling line of the group with which it is associated.

Cut-off relay C0 of line circuit X also hav- I ing denergized and restored its contacts to normal, all parts of the linecircuit X are again at normal and areavailable for 'another connection. -Now, returning to the release of the selector U,

noted that a locking circuit for release relay RR is established upon its energization, through a contact 147, primary off-normal contact 97, the winding of relay PRR, to the live pole of battery B thus energizing the relay PRR also. A circuit through the release magnet is now established from ground at contact 98 of relay .PRR, through alternate contact 99 of release relay RR,

, the winding of said release magnet RM to the live poleof battery B energizing the said release magnet, and due to the mechanical construction of theswitch, the wipers and off-normal contacts are restored to their normal position. At the time the calling subscriber restores his telephone to its hook and denergizes the rela s PR and SR, the

circuit through the win ing of relay 136 is broken at contact 137 of secondary relay SR, thus allowing the relay 136 to deenergize. This has no material effect upon the releasing circuit just described, although it serves to furnish a multiple path from batteryB, through resistance coil 148, contact 149, contact 150 of relay RVR, and the winding of and restored to normal. 'It will now be noted that all the apparatus included in the line circuit X, line selector Q, and first selector U, have been restored .to normal and are available for use in making another connection. The second selector V is also released at the time the calling subscriber 'restores hi telephone in the following manner.- Returnin now to that point in the release of the rst selector U, at which the release relay RR first became energized,

' it will be noted that a circuit is established from the live pole of battery B ,'through the resistance coil 151, alternate contact 101 of release relay RR, contact 102 of release magnet RM, wiper 34, bank contact 37, contact 152 of the rimary off-normal switch PON and the wmding of release relay BB to ground, thus energizing the said release relay BB of the second selector V. vThis energizing circuit is only of short duration, since as soon as enough time has elapsed for the release relay RR of the first selector U, relay PRR and release ma et RM, to energize in the order named, t e energizing circuit for release relay BB is broken at con-' tact 102 of release magnet RM. As in the first selector, the energization of release relay. RR of the second'se'lector establishes a locking circuit through contact 153,

primary off-normal 107 and the winding of relay lERR tothe live pole of battery B thus energizing the relay PRR. As in the first selector, a release circuit is now established from ground at alternate contact 108, through alternate contact 109, and the wind ing 9f release magnet RM to the live pole circuit for the release magnet RM is broken at alternate contact 109 of release relay RR, and the switch and its associated parts, being thus restored to normal, are available [for another connection. As previously stated, the calling subscriber having first restored his receiver to the switch-hook, the line selector, first selector and second selector are only restored to normal. Although upon the energization of release relay RR of second selector V, an impulse of current is sent from battery B through the resistance coil 154 and on through the wiper 40 and contact 43, this has no efiect upon the connector W, as in tracing the circuit through from bank contact 43, it will be noted that a direct ground is connected thereto at alternate contact 155 of the closing relay OR. I

The called subscriber now restores his telephone to its switch-hook, and the circuit, which was established from ground at the tip relay TR, through the winding of saidrelay, out over the line and through the telephone at N, back over the line and through the impedance coil 129, to the live pole of battery B is interrupted at the switch-hook 54 and the tip relay TR is deenergized. The release relay RR is now energized by a flow of current from the live pole of battery B through resistance coil 156, normal contact 157, contact 158 of relay CR, and the winding of said release relay RR to ground, energizing the said release relay; and a locking circuit is now established for said release relay through the contact 159, con! tact 118 of primary oif-normal switch PON and the resistance coil 160, to the live pole of battery 13. The relay RR being energized, the ground is removed from normal contact 123 and the relays R and CR are deencrgized and restored to normal. The

dei nergizing of relay R breaks the circuit through relay RG at contact 125, and the said relay, and also the cut-olfrelay CO,

' which were connected in series, are restored to normal. The release relay RR being energized, the circuit is closed through the release magnet RM, from the live pole of battery B through the winding of release magnet RM to ground at alternate contact 123, energizing the said: release magnet, which, on account of the mechanical construction of the switch, restores the wipers and oil-normal springs to their normal position. The locking circuit for the release relay RR is broken at primary off-normal cont-act 118 upon the return of the connector switch to normal. The release relay, now being denergized, opens the circuit tor the release magnet RM and the connector switch W, with its associated relays and mechanism, is restored to normal and is available for another connection. The cut ofi? relay C0 of line circuit X, being deenergized, restores the line circuit X to its normal condition and the telephone of the subscriber N is now available for another connection.

Assuming now that the called subscriber was the first to replace his telephone on its switch-hook, the previously described path through substation N would be broken at the switch-hook 54 and the tip relay TR would be deenergized, the same circuit changes would take place as before, and the connector switch W would be released and its associated parts returned to normal. As previously stated, when the called subscriber is the first one to restorehis telephone to the hook, he releases the first selector, second selector and connector. The manner in which the connector has been restored being described, I will now describe the manner in The release relay RR now becomes energized and is locked u over the path leading through the win ing of relay PRR to battery B energizing the relay PRR, which in turn establishes a release circuit for the first selector U as previously described, and a release impulse is repeated to the second selector V as before, releasing the said second selector and restoring it and its associated relays to normal. It will be noted that the relays PR and SR remaining energized, due to the circuit through the calling substation, the reversing relay RVR- remains energized, due to the locking circuit established from the ground at contact 143 of relay PR, through contact 141 and the windin of relay RVR to battery B The first selector and all its associated parts, with the exception of the three relays just mentioned, have now been restored to normal. The calling subscriber, now replacing his telephone on the switch-hook, interrupts the-circuit of relays PR and SR at the switchhook 54 and the said relays PR and SR deenergize, and a releasing circuit for the line selector switch is thereby closed through contacts 144, 145 of the relays PR and SR. The release relay RR of the line selector Q is thereupon energized in the previously described manner, releasing the line selector Q and line circuit X, and as the reversing relay RVR became deenergized upon the opening of c0ntact.143 of relay PR, all of the apparatus is now in a normal condition and is available for another connection. If, now, the calling subscriber has made connection to a busy line, the replacing of his telephone on its hook will cause the release of all the switches used in making the connection. The replacing of his telephone causes the denergization of relays PR and SR, as heretofore explained, and consequently the first selector U and line selector Q immediately return to normal and transmit a releasing impulse to the second selector V, which in turn transmits a releasing impulse from battery B Fig. 1, Part 2, through resistance coil 154, alternate contact 112 of rel/pry RR contact 111 of the release magne v wiper 40, contact 43, primary offnormal contact 116 of connector W, normal contact 155 of relay OR, and back through the winding of release relay BB to ground. The release relay RR energizes, closing a circuit for the release magnet RM, and the connector W is restored to normal in the manner previously described.

Now referring to the manner in which a subscri er may release the switches of any partially completed connection, we will assume that the calling subscribers receiver is removed from the switch-hook and replaced before the dial is moved. In this instance, the line relay LR energizes and remains locked ufitilthe line has been selected by line selector Q. This having taken place, the relays PR and SR will, of course, energize; but the subscriber having replaced his telephone on the hook, the circuit at the substation will again be interrupted at switchhook 54, the relays PR and SR will deenergize, closing a releasing circuit through the contacts 144 and 145 and releasing the line selector Q and line circuit X by a circuit extending from ground at release relay RR of the first selector U, back through the re lease relay R R of the line selector Q. Now, assuming that the calling subscriber has operated lllS dial a single time, the first selector U will, of course, operate to select an idle second selector V; and the subscriber having replaced his telephone on the switch-hook, the relays PR and SR will deencrgize, closing the release circuit through contacts 144 and 145 and restoring the line circuit X, line selector Q and first selector U to normal. If the calling subscriber has operated his dial two times, the second selector V, of course, will have been operated, and should the telephone now be restored to the switch-hook, the relays PR and SR will, of course, deenergize, releasing the line selector and first selector U, and a release impulse will be transmitted to the second selector V, restoring it to normal. Should the subscriber extend the line circuit to the connector and operate the dial the third time, causing a primary movement of the connector, and then replace 'his telephone receiver on its hook, the circuit for relays PR and SR will be broken at the switch-hook 54. releasing the line selector Q, first selector U, second selector V, and transmitting a releasing impulse from the second selector V over the wiper 40, bank contact 42, primary off-normal con tact 116, normal contact 155 of relay CR, back through the winding of release relay BB energizing the said release relay, which in turn will operate the release magnet of the connector switch W and restore it to normal. Should the subscriber complete the call and then restore the telephone before the called subscriber has answered, the switches would be released in the manner similar to that just described.

Switch construction.

It is obvious that in the telephone system just described, many different forms of switching devices may be usedto perform the dllferent functions described, but I preferably employ switches of the type illustrated in Figs. 2 to 8, inclusive. Referring to Figs. 2 and 3, which illustrate the preferred line'selector construction, MM is the motor magnet which, with its associated pawl 205, operates to step the ratchet wheel 206, with its common shaft 25, forward. 207 1s an angle iron which serves as a common means of support for the ten line selectors 1n a group. 208 is a frame which serves as a bearing at one end for shaft 25 and also upon which the bank contacts of each line selector are mounted. At 209 are shown several bank contacts, of which there would be one hundred and ten. In line selector Q, Fig. 1, Part 1, it will be noted that the lines L and L are directly connected to their respectlve wipers 28 and 29. In the actual construction of the switch, the lines are not 1 directly connected to the wipers, but are connected to the common plates 203, 204, and in this instance the wipers simply serve to connect the common plates 201. 202, 203, 204 to-their respective contacts. The wipers 26, 27, 28, 29, are securely fastened to the hub 210, which is loose upon shaft The collar 211, with arm 212, is loosely keyed to shaft by key 213 and mm'os with shaft 25 when it is stepped forward. As previresents ously stated, there would be ten banks of 0on tacts 216 and ten clutch magnets GM to each group of line selectors. These would be mounted side b side on angle iron 207 and the' wipers of t e ten line selectors would be connected to the common shaft 25. Key 214 is similar to key 213v and is the one which would connect to the second line selector.

The common shaft 25 is shown broken at its lower extremity, as is also the angle iron 207.

These may be extended to the proper length so that the ten line selector switches may be. I mounted thereon. 215 is a catch pin projecting from the hub 210 and enga ed by arm 212. Now as to the operation 0 the switch when the motor magnet M184 advances the common shafts-25fcollar 211 is carried around with the shaft and, due to the arm 212 engaging catch pin 215, the hub 210,

with its associated wipers, is also carried for- Ward with the shaft. As soon as the wipers 126, 27, 28, 29 engage a calling line, the clutch magnet will energize and move collar 211 with its arm 212 downward to disengage'the catch pin 215; and the wipers, being free from their engagement with the shaft 25, remain in connection with the selected line. It is obvious that should the motor magnet MIM advance the shaft 25 forward once more, the wipers 26, 27, 28 and 29 of the busy line selector will remain in engagement with their selected contacts so long as clutch magnet CM is energized, but wipers of the other idle line selectors will advance with the shaft to select a calling line. When the clutch magnet CM is denergized, which occurswhen the calling subscriber has restored his telephone to its switch-hook, the collar'2l1 will move upward and the arm 212 will now be in a position to engage catch pin 215 once more when it. comes around to advance the wipers 26, 27, 28 and 29'forward.

Figs. 4 to 8, inclusive, illustrate the preferred form of structure for the first and second selectors and, with a slightly different adjustment of the wipers and secondary off-normal springs, for the connectors also. The switch comprises the frame 300, the primary shaft 301, the secondary shaft 302, the wipers 34, 35, 36, primary magnet PM, secondary magnet SM, release magnet RM, the primary off-normal switch PON, secondary off-normal switch SON and ten banks of contacts, as shown at 303 in Figs. 4 and 6. The bank contacts, as shown in Figs. 4, 5 and 6, are arranged in a bank forming the segment of a sphere with the ends of the said bank contacts pointing toward the spheres center. The wipers 34, 35 and 36 are pivotally mounted on primary shaft 301,.and also have a sliding connection at 304 with the secondary shaft 302. In the lower portion of Fig. 5, a bank of one hundred sets of contacts is indicated;- For each line, whether subscribers line or trunk line,

there are three contacts 37, 38 and 39. In Figs. 4 and 6, but a single row or section of ten sets of contacts is shown, but it is to be understood that there are ten such sets for each switch. In operation, the primary magnet PM, by means of its armature and pawl 305, operates to step the ratchet wheel 306 forward to advance the wipers 34, 35 and 36 to the desired group of bank contacts. Checkpawl 307 prevents the return of the wipers until the said pawl is operated by therelease magnet RM. Upon the first step of the primary magnet, the arm 308, which is secured to the primary shaft 301, moves.

the insulated pin 309 toward the left and the primary off-normal springs PON move to their alternate position and remain so untilthe primary shaft returns to normal. Having moved the wipers opposite to the bank with which connection is desired, the secondary-magnet SM is now operated, and through the action ofits armature and pawl 310, the secondary shaft 302 is moved downward. Due to the sliding connection at 304 between the wipers and secondary shaft 302, the wipers are advanced one step upward along the row of bank contacts for each operation of the secondary magnet SM. In the operation of the secondary off-normal switch SON, it will be noted that a sliding bar 311 is located alongside of the secondary shaft 302. and bearingin the upper and Upon the first downward movement of sec-.

ondary shaft 302, block 313, being carried with it, allows the sliding bar 311 to move downward, and as the secondary off-normal springs rest upon the projection 312 at the I upper end of sliding bar 311, the springs are moved to their alternate position. They remain in this position until the shaft 302 is restored to normal. Having described the manner in'which the. switch is operated to make connection to a set of bank contacts, the method of releasing will now be considered. To release the switch and restore all its parts to their normal condition, the release magnet RM is energized and attracts its armature, and the lower extremity 314 of the armature engages the check pawl 307 and moves it out of engagement with ratchet wheel 306. The projection 315 of check pawl 307 engages the check pawl 316 and moves it out of engagement with the secondary shaft 302. The two shafts are now restored to normal, due to being under tension of their respective restoring springs 318, 319. To prevent the wipers from rubbing against the sides of the contacts in releasing, due to being under the tension of the spring 317, a small key 319 is provided upon the sliding'bar 311. Upon the first downward movement of the secondary shaft 302, the bar 311 also moves downward and shaft 301 to return to normal.

The mechanism of the connector is similar to that described in Figs. 4 to 8, inclusive, except that the wipers are adjusted so as to be two steps distant from the first set of bank contacts and the secondary off-normal springs are provided in number and adjustment as previously described and as indicated in Part 3 of Fig. 1.

In Fig. 9 of the drawing, I have shown a line circuit X and line selector switch Q which are modified in certain respects from those shown in Fig. -1. In the line selector Q}, the common shaft 25 is constantly rotated by the motor magnet MM. while in the line selector Q (Fig. l), the common shaft 25 is rotating only while moving the wipers of the idle line selectors to make connection to a calling line. And in the line circuit X there is but one relay,the cut-ofl relay CO. By using the constantly rotating shaft 25, it is possible to use a very simple line circuit. These line and line selector circuits X and Q will operate in connection with the first selector U, second selector V and connector W, the same as the circuits X and Q of Fig. 1. And in operation, the subscriber M, desirin to make a call, removes his receiver from its switch-hookand closes a circuit which may be traced from the live pole of battery B, through resistance coil 61, contact 62, conductor L out over limb S, throu h the substation and back over limb P o the line, conductor L, and contact 400 of cut-ofl' relay CO, to the multiple contact 31. As previously stated, the wipers of the different line selectors, associated with the common shaft 25, are constantly stepping around over the passive contacts of the said line selectors, and consequently as soon as the wipers 26, 27, 28, 29, of the line selector Q (assuming them to be the nearest to their passive contacts) reach their contacts 30, 31, 32, 33, battery will flow over the previously described path to contact 31, over wiper 27, through the winding of clutch magnet GM to ground at contact 69 of release relay RR, energizing the said clutch magnet CM and stopping the wipers 26, 27,

28 and 29 in engagement with the contacts 30, 31, 32 and 33 of the calling line. Upon the energization of clutch magnet CM, a circuit is established through the locking contact 70, wiper 26 and contact 30, then through the winding of cut-off relay CO to the live pole of battery B, energizing the said cut-off relay, and the two relays remain energized until their locking circuit is broken at contact 69 of'release relay .RR. The energization of cut-off relay CO breaks the initial energizing circuit for the clutch magnet CM .at contacts 400 and 62. Now,

'by placing Fig. 9 of' the drawing to the left of Fig. 1, Part 2, and the latter to the left of Fig. 1, Part 3, it will be noted that after the energization of the clutch magnet CM, the same circuitchanges take place at first selector U as described in connection with Fig. 1, Parts 1 and 2. In extending his line circuit beyond the first selector, the calling party operates his calling device 60 andthe connection is completed in the manner"described in connection with the system disclosed in Fig. 1. Parts 1, 2 and 3. At the time the line selector Q makes connection with the calling line,a busy condition, or ground, is placed upon the contact 49 to prevent any connector from making connection to that line. The circuit just referred to is traced from the ground at contact 69 of release relay R R, through the winding of pleted connection to the desired substation and conversed with the desired party, then upon replacing his telephone upon its switch-hook, the circuit for the relays PR and SR, which extended through said subscribers transmitter, is broken and said relays de'energize and establish a release circuit similar to that described in connection with Fig. 1. Upon the establishment of this circuit, release relay B B of the line selector Q} is energized and opens the circuit established from ground at 69 through the clutch magnet and the cut-off relay CO; and as a consequence, the line selector circuit Q and the line circuit X are restored to their normal condition and are available I tating shaft 25 and are now steppcdaround until stopped in connection with another calling line. It is obvious that any suitable essee? means may be used to constantly rotate shaft I 25, and I do not wish to be limited to the specific means shown.

In Fig. of the drawing, I have illustrated other modified line and line selector circuits X and Q The line selector Q differs from that of Fig. 1 in that the shaft 25 makes one complete revolution each time it is started. This is for the purpose of picking up any sets of wipers which have been disengaged from the clutch magnets after a connection has been released, so that it will require less time to make connection to a calling line after acall has been initiated. The operation of the line selector Q? in connecting to a calling lineand again releasing therefrom, is the same as that of the line selector Q of Fig. 1, except as to the operation of the added contacts 503 and 504 which are for the purpose of closing a circuit through the motor magnet M at the time of release. -The closing of this circuit causes the initial energization of the motor magnet M to advance the shaft 25 one revolution so it may pick up the wipers 26,27, 28 and 29 after they are released. The line circuit X operates the same as the line circuit X of Fig. 1. Now, placing Fig.- 10 of the drawing to the left of Fig. 1, Parts 2and 3, as heretofore, and assuming that the subscriber at substation M desires to converse with called party,'.the removal of his receiver from its switch-hook will'close a circuit from the live pole of battery B out over the line. through substation M, back over the line, through the winding of the line relay LR to ground, energizing the line relay, which is locked up in a manner similar to that described in Fig. 1 and closes a circuit from the ground at contact 66, through the winding of motor magnet 'MM, to the ungrounded side of generator G. The motor magnet MQM now operates to step the wipers 26, 27, 28, 29, to seek, connection with the calling line, and upon reaching their respective contacts 30, 31, 32, 88, an energizing circuit will be established for the clutch magnet GM which operates to disengage the wipers 26, 27, 28 and 29 from the shaft 25 and leave them in connection'with the terminals of the calling line. Upon the first step of the shaft 25, the contact spring 501, which. normally rests upon the insulated pin 502, moves out of engagement with the said pin 502 and a circuit is established from ground at con tact 505, through contact spring 501, the winding of oE-normal relay OR, to the live pole of battery B, energizing the said ofi-normal relay QR and establishing a circuit from ground at contact 500, through the winding oi? motor magnet to the ungrounded side of the grounded generator G. The circuit traced from the ground at contact 66 of the line relay LR, which iniftially energized the motor magnet MM, is broken at the time the lime selector connects with the calling line, but the ofi-normal relay OR having been energized and having established a circuit from the contact 500 through the winding of the motor magnet MM, the shaft 25, with its connected wipers, is stepped around until the insulated pin 502 again engages the spring 501, interrupting the circuit through the ofi-normal relay ()R, which in turn'interrupts the circuit from the ground at contact 500 through the motor magnet MM, and stopping the further movement of the shaft 25. When line selector Q connects to the calling line, the same circuit changes take place at the first selector U and the line selector Q as were described in connection with the selection of a line in connection with Fig. 1. After the subscriber at substation M has completed a connection and finished con versation, he replaces his receiver upon its switch-hook. This results in a releasing circuit being established through the release relay B B, which in turnopens the circuit for the clutch magnet CM and-the cut-off relay CO, and the clutch magnet in turn opens the locking circuit for the relay (3 R, and'the latter deenergizes and restoresits armaturecontacts totheir normal position. Therelease relay B B is provided with any suitable means, such as a copper sleeve over its, core, for rendering it slow to release its armature when its energizing circuit is broken. As the relay (3 R must retract its armature, thereby opening the circuit through relay B B, before the said relay B B can release, a momentary circuit is closed from the ground at contact 503 oi relay 0 R through the contact 50a of the release relay BER, then through the winding of the motor magnet MM to the ungrounded side of the generator G. The motor magnet MM then steps the shaft 25 forward, again closing a circuit from the ground at contact 505, through the winding of the ofi-normal relay QR to the live pole of battery B, whereupon the latter closes a circuit from ground at contact 500, through the motor magnet to the generator G and the shaft 25 is stepped around until the circuit through the cci f-normal. re-

lay @Ris again broken at contact 505, 501, which in turn opens the circuit through mo tor magnet Mi /i and the shaft 25 comes t its 

